System for simulating the firing of a weapon at a target

ABSTRACT

THE INVENTION CONCERNS A SYSTEM FOR SIMULATING THE FIRING OF A WEAPON, IN PARTICULAR A WEAPON MOUNTED ON A MOVABLE WEAPON CARRIER, AT A TARGET, PARTICULARLY A MOVING TARGET THE SIMULATOR SYSTEM INCLUDES A RADIATION TRANSMITTER FOR EMITTING A NARROW BEAM OF OPTICAL RADIATION, WHICH IS MOUNTED ON OR COUPLED TO THE WEAPON SO AS TO FOLLOW THE AIMING MOVEMENTS OF THE WEAPON IN AZIMUTH AND ELEVATION. THE TRANSMITTER COMPRISES A MIRROR OR SOME SIMILAR OPTICAL MEMBER DETERMINING THE EMISSION DIRECTION OF THE TRANSMITTER AND THIS MIRROR IS ROTATABLE SO THAT THE EMISSION DIRECT CAN BE MOVED IN AZIMUTH AS WELL AS IN ELEVATION BY CORRESPONDING ROTATION OF THE MIRROR. BEFORE THE INSTANT WHEN THE FIRING OF A PROJECTILE WITH THE WEAPON AT THE TARGET IS SIMULATED, THE MIRROR IS LOCKED IN A PREDETERMINED POSITION SUCH THAT THE EMISSION DIRECTION OF THE TRANSMITTER IS PARALLEL TO THE DIRECTION OF FIRE OF THE WEAPON. AT THE INSTANT OF A SIMULATED FIRING OF A PROJECTILE THIS LOCKING IS RELEASED AND THE MIRROR BECOMES GYROSTABILIZED SO AS TO BE INDEPENDENT OF ANY SUBSEQUENT MOVEMENTS OF THE WEAPON. IN ITS GYRO-STABILIZED UNLOCKED STATE THE MIRROR IS ALSO COUPLED TO A SERVOMOTOR FOR ROTATION OF THE MEMBER IN A DIRECTION CAUSING A CHANGE OF THE EMISSION DIRECTION OF THE TRANSMITTER IN ELEVATION. A COMPUTER UNIT IN THE SYSTEM COMPUTES THE PROPER GRAVITY CORRECTION ANGLE OR SUPERELEVATION ANGLE OF THE WEAPON FOR THE FIRING OF A REAL PROJECTILE AT THE TARGET AND PRODUCES A SIGNAL PROPORTIONAL TO THIS COMPUTED GRAVITY CORRECTION ANGLE. THIS SIGNAL IS SUPPLIED TO SAID SERVOMOTOR SO THAT THE GYROSTABILIZED EMISSION DIRECTION OF THE RADIATION TRAMSMITTER IS LOWERED IN ELEVATION THROUGH AN ANGLE EQUAL TO THE COMPUTED GRAVITY CORRECTION ANGLE. THE COMPUTER UNIT COMPUTES ALSO THE TIME OF FLIGHT TO THE TARGET FOR A REAL PROJECTILE AND AFTER A TIME INTERVAL EQUAL TO SAID COMPUTED TIME OF FLIGT AFTER THE INSTANT OF THE SIMULATED FIRING OF A PROJECTILE THE COMPUTER UNIT ACTIVATES THE RADIATION TRANSMITTER TO EMIT A SHORT PULSE OF RADIATION. ON THE TARGET RADIATION SENSITIVE RECIEVING MEANS ARE PROVIDED FOR DETECING ANY RADIATION PULSES RECEIVED AT THE TARGET FROM THE RADIATION TRANSMITTER ON THE WEAPON.

R. T. l. ERHARD Oct. 5, 1971 SYSTEM FOR SIMULATING THE FIRING OF AWEAPON AT A TARGET 2 Sheets-Sheet 1 Filed Dec. 23, 1969 RUNE TORSTENlS/DOR ER/MRD Oct. 5, 1971 R. T. l. ERHARD SYSTEM FOR SIMULATING THEFIRING OF A WEAPON AT A TARGET 2 Sheets-Sheet 2 Filed Dec. 23, 1969 HY CA T TDRNE 15 United States Patent US. Cl. 35-25 1 Claim ABSTRACT OF THEDISCLOSURE The invention concerns a system for simulating the firing ofa weapon, in particular a weapon mounted on a movable Weapon carrier, ata target, particularly a moving target The simulator system includes aradiation transmitter for emitting a narrow beam of optical radiation,which is mounted on or coupled to the Weapon so as to follow the aimingmovements of the weapon in azimuth and elevation. The transmittercomprises a mirror or some similar optical member determining theemission direc tion of the transmitter and this mirror is rotatable sothat the emission direction can be moved in azimuth as well as inelevation by corresponding rotation of the mirror. Before the instantwhen the firing of a projectile with the weapon at the target issimulated, the mirror is locked in a predetermined position such thatthe emission direction of the transmitter is parallel to the directionof fire of the weapon. At the instant of a simulated firing of aprojectile this locking is released and the mirror becomesgyrostabilized so as to be independent of any subsequent movements ofthe weapon. In its gyro-stabilized unlocked state the mirror is alsocoupled to a servomotor for rotation of the member in a directioncausing a change of the emission direction of the transmitter inelevation. A computer unit in the system computes the proper gravitycorrection angle or superelevation angle of the weapon for the firing ofa real projectile at the target and produces a signal proportional tothis computed gravity correction angle. This signal is supplied to saidservomotor so that the gyrostabilized emission direction of theradiation transmitter is lowered in elevation through an angle equal tothe computed gravity correction angle. The computer unit computes alsothe time of flight to the target for a real projectile and after a timeinterval equal to said computed time of flight after the instant of thesimulated firing of a projectile the computer unit activates theradiation transmitter to emit a short pulse of radiation. On the targetradiation sensitive receiving means are provided for detecting anyradiation pulses received at the target from the radiation transmitteron the weapon.

In order that military combat practices may be carried out in arealistic manner without risks for the personnel and the equipmenttaking part in the practice there is a great need of a system forsimulating the firing of a weapon, such as a gun or a missile launcher,which is positioned in the terrain or mounted on a movable weaponcarrier, at a target, in particular moving targets, such as tanks, othervehicles, landing crafts etc. Especially there is a need of a system forsimulating combat between tanks. In order to make it possible to carryout combat field practices in a manner as realistic as possible such asimulator system must be so designed that it does not prevent the targetand the weapon with its crew acting in a manner that would be naturaland necessary in genuine combat. Further it must be designed to indicateimmediately, whether a simulated projectile fired by the weapon wouldhave hit the intended target in the real case. Further, the simulatorsystem must give evidence not only to the skill and precision of thecrew of the weapon but also of the ice accuracy and the reliability ofthose directing and aiming means that the weapon may be provided with,such as sighting instruments, lead angle computers, control servos forthe laying of the weapon etc.

For simulator systems for the purpose mentioned above it has beensuggested in the prior art to replace or simulate a real projectilefired by the Weapon with a pulse of radiation Within the optical wavelength range, for instance from a laser, which is emitted from theweapon in a direction dependent on the direction of the weapon and whichif hitting the intended target actuates a radiation sensitive receiverdevice mounted on the target which indicates in some suitable mannerthat it has received a radiation pulse emitted from the weapon.Simulator systems based on this principle are described for instance inthe US. patent specifications 3,143,811 and 3,243,896. Prior artsimulator systems of this general type do not, however, permit a reallyrealistic combat practice in the field and especially not practices withmoving targets and weapons mounted on moving weapon carriers, as forinstance tank combat practices. The reason for these deficiencies in theprior art systems is primarily that in these systems due considerationis not taken to the facts that an optical radiation pulse has a straightpath of propagation whereas a real projectile has a curved trajectoryand that the propagation time for an optical radiation pulse from theweapon to the intended target is negligible as compared with the time offlight of a real projectile. Moreover, it has not been taken intoaccount that in genuine combat and in particular at a weapon mounted ona movable weapon carrier one wishes generally to change the direction ofthe weapon and often also the position of the weapon as soon as aprojectile has been fired.

The object of the present invention is therefore to provide an improvedsystem for simulating the firing at a target, in particular a movabletarget, with a weapon which can be laid in azimuth and elevation, inparticular a weapon mounted on movable weapon carrier, which systemcomprises a radiation transmitter for emitting a narrow beam of opticalradiation mounted on or coupled to the weapon so as to follow the aimingof the weapon in azimuth and elevation, means for activating saidradiation transmitter to emit a short pulse of radiation a predeterminedtime interval after a manually initiated signal simulating the firing ofa projectile with the weapon, and a radiation sensitive receiver devicemounted on the target for indicating radiation pulses that may berecaived at the target. The expression optical radiation is in thepresent connection intended to encompass radiation within the infrared,visible and ultraviolet wavelength ranges.

Characteristic for the simulator system according to the invention isthat the radiation transmitter includes a member for determining thedirection of emission of the transmitter, which member is rotatable formoving said direction of emission in azimuth as well as in elevation andmay be locked in a predetermined attitude relative to the weapon suchthat the direction of emission of the transmitter is parallel to thedirection of fire of the weapon and in its unlocked state isgyrostabilized and coupled to a servo-motor for rotation of the memberin a direction causing movement in elevation of the direction ofemission in accordance with a control signal supplied to saidservomotor, and that computing means are provided for computing the timeof flight of a real projectile fired by the weapon at the target and theproper gravity correction or superelevation angle for the weapon whenfiring at the target and for producing a signal proportional to saidsuperelevation angle, said computer being adapted in response to themanually initiated signal simulating the firing of a projectile torelease the locking of said member determining the direction of emissionof the radiation transmitter and to apply the signal proportional to thecomputed superelevation angle as a control signal to said servomotor'andtoactivate' said radiation transmitter after a time interval equal tothe computed time of flight of a real projectile.

As in the simulator system according to the invention the radiationtransmitter is mounted on or coupled to the weapon so as to follow theaiming of the weapon in azimuth and elevation and the gyro-stabilizedmember in the radiation transmitter determining the direction ofemission of the transmitter in azimuth as well as elevation is normallylocked in such a position relative the weapon that the direction ofemission of the transmitter is parallel to the direction of fire of theWeapon, the direction of emission of the transmitter will coincide withthe direction of fire of the weapon at the instant when the firing of aprojectile is simulated, for instance in that the firing button of theweapon is depressed. Therefore, the emission direction of the radiationtransmitter will suffer from exactly the same errors as the direction ofthe Weapon, whether these errors are caused by errors of the crew whenaiming the weapon, errors in the superelevation angle and lead angleestimated by the crew or partially or entirely computed by a firecontrol device belonging to the weapon, or by inaccuracies in thesighting and aiming means of the weapon. As at the instant of thesimulated firing of a projectile the locking between the weapon and themember determining the emission direction of the radiation transmitteris released and said member is thereafter gyrost'abilized, the emissiondirection of the transmitter will not be affected by any movements ofthe Weapon in azimuth or elevation subsequent to the instant of thesimulated firing of a projectile. As furthermore the computer includedin the system computes the proper superelevation angle for firing a realprojectile at the target and by means of the servomotor coupled to thegyro-stabilized member determining the emission direction reduces theelevation of said emission direction of the transmitter exactly throughsaid computed superelevation angle and also computes the correct time offlight to the target for a real projectile and activates the transmitterto emit a radiation pulse no until after said time of flight, theemitted radiation pulse will hit the target and activate the radiationsensitive receiver device on the target only under the provision thatthe weapon was aimed correctly at the instant for the simulated firingof a projectile. If on the contrary the aiming of the weapon wasincorrect at said instant or if the target has moved during the computedtime of flight of a real projectile in some other way (with a difierentspeed or in a different direction) than presumed by the weapon crew orthe fire control computer, the emitted radiation pulse will not hit thetarget and thus not actuate the radiation sensitive receiver on thetarget.

In the following the invention will be further described with referenceto the accompanying drawing, in which FIG. 1 illustrates schematicallythe basic principle of the simulator system according to the invention;

FIG. 2 is a simplified perspective view of an embodiment of a radiationtransmitter shown only by way of example, which can be used in asimulator system according to the invention; and

FIG. 3 shows only by way of example a block diagram for an embodiment ofthe computer, which may be used in a simulator system according to theinvention for cooperation with the radiation transmitter shown in FIG.-2.

FIG. 1 shows schematically a tank 1 provided with a simulator systemaccording to the invention for simulating the firing of the gun of thetank 1 at a moving target 2 consisting of another tank. It is assumedthat the target 2 moves in the direction 3 with a certain speed. Thecrew in the tank 1 acts exactly in the same Way that they would do ingenuine combat, that is they observe the target 2 by means of thesighting instrument in the tank and estimate or compute by means of thefire control aids, such as range meter, lead angle computer and similardevices, that may be provided in the tank, the direction that the gunbarrel 4 of the tank shall have in order to hit the target 2 with a realprojectile. Assume for instance that it is estimated or computed that ata certain instant the barrel 4 should be aimed at the point 6 in orderthat a projectile tired at said instant shall hit the target 2. Thedirection to this aiming point 6 deviates from the direction to thetarget 2 at the instant of firing, firstly by the lead angle which isdependent on the speed and the direction of movement of the target 2',the range to the target and the time of flight of a real projectile tothe target, and secondly by a superelevation angle or gravity correctionangle which depends on the curved trajectory of the real projectile. Ifthe position of the aiming point 6 has been estimated or computedcorrectly and the gun barrel 4- of the tank 1 is aimed properly at theaiming point 6, a real fired projectile would due to the movement of thetarget 2 during the time of flight of the projectile and to the curvedtrajectory 7 of the projectile hit the target 2 in the point of impact8. If on the contrary there exists some error in the computation orestimation of the position of the aiming point '6 or in the aiming ofthe barrel 4 at the aiming point at the instant of firing, a real firedprojectile would not hit the target 2.

For simulating a real fired projectile the system according to theinvention includes an optical radiation transmitter 9 so mounted on thetank 1 that it participates in or follows the movements of the gunbarrel 4 in azimuth as well as elevation. As in the illustrated exampleof the invention the tank 1 is assumed to be of the type in which thegun barrel 4 is fixed in the tank body and consequently is aimed bymovements of the entire tank body, the radiation transmitter 9 ismounted directly upon the upper surface of the tank body. If instead thetank were provided with a rotatable gun turret with the gun barrelmounted for elevation therein, the radiation transmitter 9 would insteadbe mounted on a part of the gun which is aimed in azimuth as well as inelevation or coupled to such a part of the gun so as to follow theaiming movements of the barrel. The radiation transmitter 9 includes amember determining the direction of emission of the radiation, whichmember is movable or adjustable for variation of the emission directionin azimuth as well as elevation. During the aiming of the barrel 4 atthe estimated or computed aiming point 6, however, said member in theradiation transmitter 9 is locked in such a position that the emissiondirection 10 of the transmitter is parallel to the direction 5 of. thebarrel 4. Thus, also the emission direction 10 of the radiationtransmitter 9 will be aimed at the estimated or computed aiming point 6.At the instant of firing, that is when the tank crew indi cates orsimulates the firing of a projectile at the target 2, for instance bydepressing the firing button of the gun, the locking of the member inthe transmitter 9 determining the emission direction is released and asthis member is gyro-stabilized in its unlocked state, the emissiondirection 10 will not after the firing instant be affected if thedirection of the barrel 4 should be changed in azimuth and/or elevation,for instance while the tank crew aims the gun in a new direction forfiring a new projectile at the same or another target. On the otherhand, however, the member in the transmitter 9 determining the emissiondirection 10 of the transmitter is controlled from a computer unit 11 insuch way that the emission direction 10 is lowered in elevation throughan angle corresponding to the correct supereievation angle or gravitycorrection angle for the firing at the target 2, which angle has beencomputed by the computer unit 11. After a time interval after thesimulated firing instant equal to the correct time of flight to thetarget 2 for a real projectile, which time of flight is also computed bythe computing unit '11, the computer unit 11 activates the transmitter 9to emit a short pulse of radiation. It is appreciated that thisradiation pulse will hit the target 2 in the point 8, if the crew in thetank 1 or the fire control system in the tank has estimated or computedresp. the position of the aiming point 6 correctly and the barrel 4 wasaimed properly at said point at the instant of the simulated firing. Inany other case the emitted radiation pulse will obviously not hit thetarget 2. The target is provided with a radiation sensitive receivingdevice, for instance comprising one or several radiation sensitiveelements 12, such as photodetectors, mounted on the target 2 so as to beactivated by radiation from the transmitter 9 incident upon the vulnerable portions of the target 2. This receiver device indicates, forinstance by means of light, sound or smoke signals, that it has receiveda radiation pulse emitted by the transmitter 9.

For a realistic simulation of a duel between two tanks 1 and 2 anadditional simulator system according to the invention is obviouslynecessary, which has its transmitter and its computer unit mounted onthe tank 2 and its radiation sensitive receiver device mounted on thetank 1.

As mentioned in the foregoing, the computer unit in the simulator systemhas to compute firstly the correct superelevation angle for firing atthe target and secondly the time of flight to the target for a realprojectile. Using the symbols:

V =the muzzle velocity of the projectile =the mean velocity of theprojectile D:the range to the target t =the time of flight of theprojectile U the superelevation or gravity correction angle,

one has obviously tf=D/V As known to those skilled in the art the meanvelocity of the projectile can be expressed by the series V =V c D+c D-}-c D (2) For most types of ammunitions a suflicient accuracy isachieved with the three first terms in this series and for projectilevelocities well above twice the speed of sound the first two terms aresufficient.

As also known in the art the superelevation angle may be approximatedwith sufficient accuracy by the series in which generally one or twoterms are sufiicient for good accuracy. In the expressions (2) and (3)the quantities c c 0 etc. and k k k etc. are constants.

For a correct computation of the superelevation angle U and the time offlight t the computer unit needs obviously information about the actualrange D to the target. This information can be supplied to the computerin several different ways. In a simple embodiment of the invention theinformation about the range to the target may be supplied to thecomputer from the training supervisors that are generally always presentat field practices, for instance from a supervisor who sits on the tankand has a suitable range meter. In this case the range value can be fedinto the computer of the simulator system manually by said supervisor.Alternatively, correct range values can be supplied to the computer overa remote data transfer link. In a more sophisticated system according tothe invention the system itself may be provided with its own rangemeter, as for instance a radar range meter, a laser range meter or someother type of electronic or optoelectronic range meter, from which thecomputer is continuously supplied with information about the correctrange to the target. If a range meter operating with optical signals isused, the optical signals from the range meter must of course haveanother frequency than the radiation pulses from the transmitter 9 usedfor simulating real projectiles. If a simulator system according to theinvention is to be used together with a weapon which is provided withits own accurate range meter, information about the range to the targetmay of course be obtained from this range meter, wherefore the simulatorsystem does not have to be provided with any range meter of its own.

FIG. 2 shows schematically and in a perspective view a preferredembodiment of the radiation transmitter 9. This includes a casing 35shown very schematically only, which is mounted on the weapon or coupledto this in such a way that it follows the movements of the weapon inazimuth as well as in elevation. Inside the casing 35 there is asuitable radiation source 13, as for instance a laser, a luminescencediode, a laser diode or a xenon lamp, which can be activated to emit ashort pulse of radiation. The radiation from the radiation source 13 isby a suitable optical system, including for instance a condensor 14, adiaphragm 15 and an objective 16, directed as a narrow radiation beamtowards a mirror 17, which deflects the radiation beam through an exitopening 18 in the front wall of the casing 35. Consequently, thedirection of emission 10 is determined by the mirror 17 which isuniversally pivoted about a stationary point in the casing 35 so thatthe emission direction 10 can be moved in azimuth as well as inelevation by variation of the attitude of the mirror 17.

For this purpose the mirror 17 is supported for rotation about an axisSS in a frame 19, which in its turn is supported for rotation about anaxis HH in two stands 20 and 21 which are stationary in the transmittercasing 35. The two axes SS and HH are mutually perpendicular and it isassumed that the transmitter casing 35 is mounted in such an attitudethat the axis HH is normally parallel to the elevation axis of the gunbarrel, whereas the axis SS is normally parallel to the azimuth or trainaxis of the barrel.

By rotation of the frame 19 about the axis HH it is consequentlypossible to move the emission direction 10 in elevation, whereas byrotation of the mirror 17 about the axis SS the emission direction 10can be moved in azimuth. The mirror 17 and thus also the emissiondirection 10 can be kept gyro-stabilized independent of the movements ofthe transmitted casing 35 and thus of the member supporting thetransmitter casing by the aid of a gyro-stabilized platform 22 which issupported by the frame 19 and rotatable in this about an axis SS whichis parallel to the axis S S. In conventional manner the gyro-stabilizedplatform 22 is provided with two angular velocity sensing gyros G and Gso mounted on the platform 2 2 that the one gyro G senses the angularvelocity of the platform 22 relative to the inertial space about theaxis S'S' and produces a signal proportional to this angular velocity,whereas the second gyro G senses the angular velocity of the platform 22about the axis HH and produces a signal proportional to this angularvelocity. The output signal from the gyro G can in conventional mannerbe applied as a control signal to a servomotor M which is stationary inthe transmitter casing 35 and coupled to the frame 19 for rotationthereof about the axis HH, whereas the signal from the gyro G can beapplied as a control signal to a servomotor M which is coupled to theplatform 22 for rotating this about the axis SS. When the signals fromthe gyros G and G are applied as control signals to the servomotors Mand M respectively, the platform 22 is, as well known in the art,maintained stabilized in space about the two axes HH and S'S'.

The gryo-stabilized platform 22 is coupled to the mirror 17 through theframe 19 and also through a link system including two rigid links 23 and24. The one end of the link 23 is attached to the gyro-stabilizedplatform 22, whereas the one end of the link 24 is attached to themirror 17. The opposite end of the link 24 is shaped as a fork 24ahaving a straight groove pointing at the pivot centre of the mirror 17.The opposite end of the link 23 is provided with a pin 23a which isdisplaceable in the fork-shaped end 24a of the link 24. The frame 19 andthe gyro-stabilized platform 22 are positioned in the transmitter casing35 in such a manner that the axis HH is parallel to the radiation beamincident upon the mirror 17 from the radiation source 13 and that thedistance between the pivot centre of the platform 22 and the pivotcentre of the mirror 17 is equal to the distance from the pivot centreof the platform to the outer end of the link 23. It is appreciated thatthis connection between the gyrostabilized platform 22 and the mirror 17has as a result that a given angular rotation of the platform 22 aboutthe axis S'S' causes an exactly equal angular rotation of the emissiondirection 10 about the axis -5 and that a given angular rotation of theplatform 22 about the axis HH causes an exactly equal angular rotationof the emission direction about said same axis. Consequently, theemission direction 10 follows exactly the position of the platform 22and if the platform 22 is gyro-stabilized relative to the support of thetransmitter the emission direction 10 of the transmitter will also begyro-stabilized relative to said support.

As mentioned in the foregoing, however, the emission direction 10 andthus the mirror 17 shall normally be locked relative to the transmittercasing 35 and thus relative to the direction of fire of the weapon insuch an attitude that the emission direction 10 is parallel to thedirection of fire of the weapon. In the illustrated embodiment of theinvention this is achieved in that the platform 22 is locked in acorresponding attitude by means of the servomotors M and M For thispurpose a position signal generator, such as a potentiometer, P and Prespectively is coupled to each of the servomotors M and M respectivelyso as to produce a signal with a magnitude and a polarity dependent uponthe angular deviation of the platform 22 about the axis S'S' and theaxis HH respectively from the predetermined desired locking posi tion.The electrical connection is shown in FIG. 3, that is the output signalsfrom the position signal generators P and P are through switches 25 and26 and the servoamplifiers 27 and 28 applied as control signals to theservomotors M and M respectively. It is appreciated that with thisconnection the two servomotors will automatically maintain the platform22 and thus also the mirror 17 and the emission direction 10 in thedesired locked position, in which the output signals from the twoposition signal generators P and P are zero. The object of the switches25 and 26 will be discussed in further detail in the following.

FIG. 3 shows, also by way of example, the circuit diagram for anembodiment of the computer 11:. This includes two signal multiplicators,in the illustrated example consisting of potentiometers P1 and P2, whichare set in agreement with the range D to the target in some of themanners discussed in the foregoing. The potentiometer P1 is suppliedwith a constant voltage, which for the sake of simplicity is assumed tohave the value 1, whereas the potentiometer P2 is supplied with theoutput voltage from the potentiometer P1. Consequently, P1 produces asignal proportional to the range D to the target, whereas thepotentiometer P2 produces an output signal proportional to D These twosignals are connected to separate inputs of an amplifier 29. Thisamplifier is also supplied with a constant signal, which for the sake ofsimplicity is assumed to have the value 1. These input signals areamplified and summed in the amplifier 29 with the proportionalityconstant k k and k respectively so that the output signal of theamplifier 29 is proportional to the first three terms in the seriesexpression (3) for the gravity correction angle U. This output signal isconnected to a signal comparator 30, to which also the output signalfrom the gyro G is applied but with the opposite polarity as comparedwith the signal from the amplifier 29. The computer 11 includes also asecond amplifier 31 which is supplied with the signals proportional to Dand D respectively from the two potentiometers P1 and P2 and also with asignal proportional to the muzzle velocity V of a real projectile. Thesethree input signals are amplified and summed in the amplifier 31 withsuch polarities and in such proportions that the output signal from theamplifier 31 corresponds to the three first terms in the expression (2)for the mean velocity V of the projectile. The output signal from theamplifier 3'1 proportional to V is applied to a signal division circuit32 which is also supplied with the signal proportional to D from thepotentiometer P1 and which is adapted to produce an output signalproportional to D/V that is a signal proportional to the time of flightI to the target for a real projectile. This output signal is supplied toa suitable timing device 33, such as an electric timer circuit, anelectro-mechanical timer or similar, so that the time span of thistiming device is adjusted to be equal to the computed time of flight IThe timing device 33 can be started in that a switch 34 manuallyoperated by the tank crew, for instance the firing button for the tankgun, is closed temporarily.

When the timing device 33 starts, it actuates the two switches 25 and 26so that these are switched to their opposite positions. In this way thelocking of the gyrostabilized platform 22 and thus of the mirror 17 andthe emission direction 10 is released. Instead the output signals fromthe gyros G and G are connected to the servomotors M and M respectively,whereby the platform 22 and thus also the mirror 17 and the emissiondirection 10 of the transmitter become gyro-stabilized and independentof any subsequent movements of the tank in azimuth or elevation. As,however, the output signal from the amplifier 29 is connected to thesignal comparator 30 with the opposite polarity to the signal from thegyro G the servomotor M will obviously rotate the platform 22 and thusalso the mirror 17 and the emission direction 10 of the transmitterabout the axis HH with an angular velocity relative to the inertialspace which is proportional to the magnitude of the signal from theamplifier 29. At the end of the time span of the timing device 33, whichis proportional to the computed time of flight I of a real projectile,the emission direction 10 of the transmitter has consequently beenlowered in elevation through an angle exactly equal to the correctgravity correction angle U for the firing of a real projectile at thetarget. When the timing device 33 runs out after the time of flight t ofthe projectile, the timing device 33 activates the radiation source 13in the transmitter 9 to emit a short pulse of radiation. Immediatelythereafter the timing device 33 actuates again the switches 25 and 26 sothat they are returned to the positions illustrated in FIG. 3. Thiscauses the servomotor M and M to return the platform 22 and thus alsothe emission direction 10 of the transmitter to the predeterminedlocking position, in which the emission direction 10 is parallel to thedirection of the gun barrel 4, whereby the simulator system is preparedfor a simula tion of the firing of a new projectile.

It is appreciated that also various other embodiments of a simulatorsystem according to the invention are possible. Thus, for instance theradiation transmitter may be designed in various ways. Essential is onlythat the emission direction of the transmitter can be locked relative tothe weapon so as to be parallel to the direction of fire of the weapon,but that this locking can be released and that the emission directionthereafter in its unlocked state is gyro-stabilized and independent ofany movements of the weapon and/or the support of the weapon. In saidgyro-stabilized unlocked state it must, however, be possible to move theemission direction of the transmitter through a predetermined angle fromits initial position in response to the operation of the computer unitin the system.

Of course, also the computer unit can be designed in various ways by theuse of various types of computer components and various mathematicalexpressions for the computation of the gravity correction angle and thetime of flight. It is also appreciated that the computer may be designedto compute not only the proper gravity correction angle for the firingat the target but also the proper correction angles necessary forinstance due to wind forces upon the real projectile and the rotation ofthe real projectile. The computer may also be designed to take intoconsideration any tilt of the elevation axis of the gun barrel at theinstant of firing. If the computer unit is amplified in some of theserespects, it must compute necessary correction angles for the emissiondirection of the radiation transmitter in elevation as well as inazimuth, wherefore the computer must actuate the member in the radiationtransmitter determining the emission direction for variation of theemission direction in elevation as well as in azimuth.

Finally, it shall be pointed out that the simulator system is notdisturbed by any changes of the train angle or the elevation angle ofthe weapon subsequent to the instant of the simulated firing of aprojectile, that is during the computed time of flight for a realprojectile, but that a certain disturbance of the operation of thesimulator system will appear if the weapon and thus also the radiationtransmitter should during said time interval move from its position atthe instant of the simulated firing of a projectile. As normally,however, the Weapon is stationary at the instant of firing and hardlycan change its position in the terrain in any significant extent duringthe short time of flight of the projectile, which is of the order of lto 2 seconds, any disturbances of this type in the operation of thesimulator system will be extremely small.

What is claimed is:

1. A system for simulating the firing of a weapon (4), comprising: aweapon mounted on a movable weapon carrier, a moving target, a radiationtransmitter (9) for emitting a narrow beam of optical radiation coupledto the weapon so as to follow the movements in azimuth and elevation ofthe direction of fire of the weapon, means for activating said radiationtransmitter to emit a short pulse or radiation a predetermined timeinterval after a manually initiated signal simulating the firing of theweapon, and radiation sensitive receiving means (12) on the target fordetecting radiation pulses received at the target, said radiationtransmitter includes a member (17), responsive to a pulse of radiationfrom a radiation source within the transmitter, for determining theemission direction (10) of the transmitter, said member being rotatablefor moving said emission direction in azimuth as well as elevation,means for releasably locking said member in a predetermined positionrelative to the weapon such that the emission direction of thetransmitter is parallel to the direction of fire of the weapon, gyromeans (G G located within said transmitter for stabilizing said memberwhen in its unlocked state, and servomotor means (M for rotating saidmember in a direction causing a movement of the emission direction ofthe transmitter in elevation in agreement with a control signal suppliedto said servomotor means, and a computing means (11) adapted to receiveinformation relative to target distance and velocity of an actuallyfired projectile, to be simulated are provided for computing the time offlight (t for a real projectile fired with the weapon at the target andthe proper gravity correction angle (U) for the weapon when firing areal projectile at the target and for producing a signal proportional tosaid gravity correction angle, said computing means being adapted inresponse to said manually initiated signal simulating the firing of aprojectile to release the locking of said member (17) and connect saidsignal proportional to the computed gravity correction angle as acontrol signal to said servomotor means (M and to activate saidradiation transmitter after a time interval equal to said computed timeof flight.

References Cited UNITED STATES PATENTS 3,143,811 8/1964 Tucci et al.3525 3,243,896 4/1966 Immarco et al 3525 3,452,453 7/1969 Ohlund 3525FOREIGN PATENTS 1,114,094 5/1968 Great Britain 3525 ROBERT W. MICHELL,Primary Examiner I. H. WOLFF, Assistant Examiner US. Cl. X.R. 273101.1

